cf 168 k-Multiple Free Set bin_search

     一开始写的是逆序的，WA了，改成正序AC，想来没有道理，细看后才发现是改了当前值，让二分序列不再有序……o(╯□╰)o，正序只能是侥幸罢了

/*
author:jxy
lang:C/C++
university:China,Xidian University
**If you need to reprint,please indicate the source**
*/
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#define INF 1E9
using namespace std;
int q[100010];
int abs(int a){return a>0?a:-a;}
int bin(int l,int r,long long x)
{
    int mid;
    if(x>abs(q[r]))return -1;
    while(l<r)
    {
        mid=l+((r-l)>>1);
        if(abs(q[mid])<x)l=mid+1;
        else r=mid;
    }
    if(q[l]==x)return l;
    else return -1;
}

int main()
{
    int n,k;
    scanf("%d%d",&n,&k);
    int i;
    for(i=0;i<n;i++)
        scanf("%d",&q[i]);
    sort(q,q+n);
    int ans=0;
    for(i=n-1;i>=0;i--)
    {
        if(q[i]<0)continue;
        ans++;
        if(q[i]%k==0)
        {
            r=bin(0,i-1,q[i]/k);
            if(r!=-1) q[r]=-q[r];//一开始这是-1
        }
    }
    printf("%d\n",ans);
}